electrical engineering Mcqs
1. economics of power generation2. analog electronics3. solid state switching circuits4. parallel circuits5. switchgear and protection6. op amp circuits7. transistor audio power amplifiers8. electrostatics9. heating and welding10. multi stage transistor amplifiers11. passive filters12. network theorems13. regulated d c power supply14. a c fundamentals circuits and circuit theory15. electromagnetic induction16. power electronics17. magnetism and electromagnetism18. transformers19. modulation and demodulation20. d c generators21. semiconductor theory22. single phase induction motors23. semiconductor diode24. hybrid parameters25. digital electronics26. oscillators27. earthing or grounding28. single stage transistor amplifiers29. d c motors30. transistor biasing31. amplifiers with negative feedback32. basic electrical33. electronic instruments34. synchronous motors35. field effect transistors fet36. magnetic circuit37. control systems38. industrial drives39. power generation40. series parallel circuits41. transistor tuned amplifiers42. electrical engineering materials43. rectifiers and converters44. integrated circuits45. scr silicon controlled rectifiers46. cables47. polyphase induction motors48. measurement and instrumentation49. transistors50. electrical machine design51. electrolysis and storage of batteries52. electric traction53. transmission and distribution
6001. Under which of the following conditions hunting of synchronous motor is likely to occur?
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A. Over-loading for long periods

B. Small and constant load

C. Periodic variation of load

D. Over-excitation

6002. Mostly, synchronous motors are of_____________?
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A. induction type machines

B. smooth cylindrical type machines

C. salient pole type machines

D. alternator type machines

6003. In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately
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A. six times

B. nine times

C. one-third

D. thrice

E. twice

6004. The back e.m.f. of a synchronous motor depends on______________?
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A. all of the above

B. load

C. speed

D. load angle
6005. A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed
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A. the motor continue to run in the same direction

B. the motor will run in the reverse direction

C. none of the above

D. the motor will stop

E. the winding of the motor will burn

6006. By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?
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A. By changing the supply frequency

B. By interchanging any two phases

C. By changing the applied voltage

D. By changing the load

6007. While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerating torque is produced by_____________?
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A. induction motor torque in field winding

B. induction motor torque in damper winding

C. eddy current and hysteresis torque in pole faces

D. reHetance motor torque due to saliency of the rotor

E. all of the above methods
6008. Synchronous motors are_____________?
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A. none of the above

B. essentially self-starting

C. self-starting

D. not-self starting
6009. When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop_________________?
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A. inductor motor torque

B. induction generator torque

C. synchronous motor torque

D. d.c. motor toque

E. none of the above

6010. In a synchronous motor, the maximum power developed depends on all of the following except:
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A. supply voltage

B. maximum value of coupling angle

C. rotor excitation

D. direction of rotation
6011. The power developed by a synchronous motor will be maximum when the load angle is____________?
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A. 120

B. 90

C. zero

D. 45

6012. Which of the following motors is non-self starting ?
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A. D.C. series motor

B. Wound round induction motor

C. synchronous motor

D. Squirrel cage induction motor

6013. To limit the operating temperature an electrical machine should have proper____________?
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A. current rating

B. power factor

C. voltage rating

D. speed

6014. . In a synchronous motor which loss varies with load ?
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A. Copper loss

B. Bearing friction loss

C. Windage loss

D. Core loss

6015. Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?
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A. High field current

B. Low field current

C. High core losses

D. Low short circuit ratio

6016. Which of the following losses is not dissipated by the stator core surface in a synchronous motor?
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A. Iron losses in the stator

B. Windage losses

C. None of the above

D. Eddy current losses in the conductors

E. Copper losses in the slot portion of the conductors

6017. If the field of a synchronous motor is underexcited, the power factor will be_____________?
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A. zero

B. leading

C. lagging

D. unity

6018. Which of the following losses, in a synchronous motor, does not vary with load?
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A. None of the above

B. Any of the above

C. Windage loss

D. Copper losses

6019. A synchronous motor will always stop when:______________?
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A. load in motor varies

B. supply voltage frequency changes

C. excitation winding gets disconnected

D. supply voltage fluctuates

6020. A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
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A. Er (net resultant voltage) in armature is increased

B. none of the above

C. power factor is decreased

D. Eb (back e.m.f.) becomes less than V (applied voltage)

E. speed of the motor is reduced

6021. The torque angle, in a synchronous motor, is the angle between_______________?
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A. magnetising current and back e.m.f.

B. the rotating stator flux and rotor poles

C. the supply voltage and the back e.m.f.

D. none of the above

6022. When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected______________?
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A. it runs as a reluctance motor at the same speed

B. it runs as a reluctance motor at a lower speed

C. none of the above

D. the motor stops
6023. When load on an over-excited or under excited synchronous*motor is increased, rate of change of its armature current as compared with that of power factor is___________?
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A. more

B. equal

C. twice

D. less
6024. A synchronous motor running with normal excitation adjusts to load increases essentially by increase in______________?
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A. armature current

B. back e.m.f.

C. power factor

D. torque angle

6025. The maximum power developed in a synchronous motor occurs at a coupling angle of____________?
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A. 180

B. 90

C. 30

D. 60

6026. The speed regulation of a synchronous motor is always___________?
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A. 1%

B. zero

C. positive

D. 0.50%

6027. The size of a synchronous motor decreases with the increase in___________?
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A. all of the above

B. flux density

C. speed

D. horse power rating

6028. In a synchronous motor, the damping winding is generally used to______________?
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A. reduce noise level

B. provide starting torque only

C. none of the above

D. reduce the eddy currents

E. prevent hunting and provide the starting torque
6029. A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
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A. power factor as well as armature current will increase

B. power factor as well as armature current will decrease

C. power factor will increase but armature current will decrease

D. power factor will decrease and armature current will increase
6030. If one-phase of a 3-phase synchronous motor is short-circuited, motor will ______________?
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A. will overheat in spots

B. will refuse to start

C. will not come upto speed

D. will fail to pull into step

6031. The ratio of starting torque to running torque in a synchronous motor is____________?
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A. zero

B. infinity

C. one

D. two

6032. In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on___________?
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A. load on the motor

B. d.c. excitation only

C. both the speed and rotor flux

D. none of the above

6033. The speed of a synchronous motor:
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A. decreases as the load decreases

B. none of the above

C. increases as the load increases

D. always remains constant
6034. A synchronous motor can be used as a synchronous capacitor when it is____________?
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A. under-loaded

B. over-loaded

C. over-excited

D. under-excited

6035. The rotor copper losses, in a synchronous motor, are met by____________?
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A. armature input

B. supply lines

C. motor input

D. d.c. source
6036. A three-phase synchronous motor will have_____________?
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A. two slip-rings

B. three slip-rings

C. one slip-ring

D. no slip-rings

6037. The oscillations in a synchronous motor can be damped out by_______________?
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A. oscillations cannot be damped

B. providing damper bars in the rotor pole faces

C. maintaining constant excitation

D. running the motor on leading power factors

6038. The standard full-load power factor ratings for synchronous motors are___________?
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A. unity or zero

B. unity or 0.8 leading

C. zero or 0.8 leading

D. unity or 0.8 lagging

6039. The magnitude of field flux in a 3-phase synchronous motor?
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A. varies with speed

B. varies with the load

C. remains constant at all loads

D. varies with power factor

6040. The effect of increasing the load on a synchronous motor running with normal excitation is to___________?
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A. decrease both armature current and power factor

B. decrease armature current but increase power factor

C. increase armature current but decrease power factor

D. increase both its armature current and power factor

6041. Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?
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A. All of the above

B. Stator winding to earthed frame

C. Rotor winding to earthed shaft

D. Phase to phase winding resistance

6042. The induced e.m.f. in a synchronous motor working on leading power factor will be_____________?
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A. equal to the supply voltage

B. None of these

C. less than the supply voltage

D. more than the supply voltage
6043. In which of the following motors the stator and rotor fields rotate simultaneously?
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A. D.C. motor

B. Induction motor

C. Universal motor

D. Reluctance motor

E. Synchronous motor
6044. The synchronous motor is not inherently self-starting because_______________?
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A. the rotating magnetic field is produced by only 50 Hz frequency currents

B. the force required to accelerate the rotor to the synchronous speed in an instant is absent

C. the starting device to accelerate the rotor to near synchronous speed is absent

D. a rotating magnetic field does not have enough poles

6045. As the load is applied to a synchronous motor, the motor takes more armature current because
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A. the rotor strengthens the rotating field casuing more motor current

B. the rotor by shifting its phase backward causes motor to take more current

C. the increased load has to take more current

D. the back e.m.f. decreases causing an increase in motor current

6046. In a JFET, IDSS is known as ________________?
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A. none of the above

B. drain to source current

C. drain to source current with gate shorted

D. drain to source current with gate open

6047. A JFET has high input impedance because _________________?
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A. of impurity atoms

B. none of the above

C. it is made of semiconductor material

D. input is reverse biased
6048. The constant-current region of a JFET lies between______________?
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A. pinch-off and breakdown

B. cut off and saturation

C. cut off and pinch-off

D. and IDSS

6049. A JFET is similar in operation to ___________ valve?
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A. triode

B. tetrode

C. pentode

D. diode

6050. The gate of a JFET is ___________ biased?
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A. forward

B. reverse

C. none of the above

D. reverse as well as forward